The Unix operating system includes too many commands to list them all here. There are about 500 commands in the system directory supplied by the vendor, and another 500 that were locally installed. The following is an attempt to list a few commands in a couple of functional groups. More detail is also available in normal online system documentation and in this help section; links to other help is provided here when available. Bold and italic items have additional documentation available via the man command.
You can search for commands and read documentation on neary every command using the man command.
General commands necessary to use the system and manipulate files are listed in the first help page in this section under Beginning help.
Third party vendor software packages installed locally are listed in the Software Catalog.
All commands are run by typing the name of the command followed by a space and any parameters. The command line interpretation is done by a "shell" program. Shells may have additional features to make interactive use easier.
Here are some commands in functional groups. More detail is availble in man pages or in the section linked here. (when they get written)